Antifouling composition

ABSTRACT

An antifouling coating composition useful for coating fish netting, boat hulls, lumber, roof shingles and the like to prevent the growth of algae or fungi. The composition comprises a vinyl polymer or copolymer emulsion containing a dialkyldimethyl ammonium compound with or without an alkylbenzyldimethyl ammonium compound. The preparation of the composition must be done with care in order to prevent the added quaternary ammonium compound from destabilizing the emulsion polymer. The invention also relates to articles coated with the composition to prevent the formation of algae and fungi thereon.

This is a division of application Ser. No. 304,769, filed Jan. 31, 1989,now U.S. Pat. No. 4,990,547, which in turn is a continuation-in-part ofapplication Ser. No. 153,010, filed Feb. 8, 1988, now U.S. Pat. No.4,866,106, issued Sept. 12, 1989.

FIELD OF THE INVENTION

This invention relates to an antifouling coating composition. Thecomposition is useful for coating equipment to be submerged in the sea,for example, fish nets and boat hulls, but also finds use for protectingand preserving lumber and roof shingles and the like exposed to muchrain and subject to algae and fungal growth.

DESCRIPTION OF THE PRIOR ART

The growth of algae and fungus on structures, for example, on boathulls, on fishing nets, on roofs, on patios and on lumber is unsightly.There are, however, more important failings. The hull of a boat isconsiderably less efficient when coated with algae; the drainage of aroof can be adversely affected by the presence of algae; and patios,balconies and the like can become slippery when wet if algae arepresent. In industry, fouling and plugging of water pipes, particularlyin cooling systems, can occur with algae growth, for example, in thepulp and paper mill industries. The warm temperatures in cooling systemwaters make ideal conditions for algae growth.

A hull of a boat or a walkway can be scrubbed to remove the algae but,for example, in the case of a boat, this involves removing the boat fromthe water and also a considerable amount of hard work. As a result,chemical approaches have been used. Compounds such as chlorine, organicmercury compounds, chlorinated phenols, organic bromine compounds,metallic copper and organic tin and sulphur compounds have all been usedin an attempt to reduce the growth of algae.

In the growing of fish in pens there is a marked need for abiodegradable antifouling coating for the nets that are used to pen thefish. The coating is required to prevent the growth of marine organisms,which restrict the flow of fresh tidal water through the net.

This need has been met by the use of antifouling coatings containingheavy metals, for example, metallic copper, organic tin and mercurycompounds and the like. However, heavy metal coatings areenvironmentally undesirable, particularly in the marine environmentbecause of bioaccumulation in marine life. It has been shown that theyhave an adverse effect upon shellfish beds and other coastal marinelife, even in trace amounts. As a result, the use of heavy metals is nowillegal in some jurisdictions.

In the lumber industry, wood preservatives have been used to combatfungal growth on lumber having a moisture content over 20% or which isused in marine or buried construction. Until recently,pentachlorophenols were used, but these are now regarded asenvironmentally unsafe. Other preservatives such as copper8-quinolinolate, and borax-sodium carbonate mixtures have provedunsatisfactory for such reasons as poor efficacy in wet climates, rapidleaching due to high solubility and brown staining. Accordingly, thereis a need to develop a coating for lumber which is effective over thelong term against fungal growth.

Yet a further use of antifouling compositions is in hospitals wheremedically sterile environments are required if S. aureus infections areto be avoided, and on hard surfaces, such as, concrete.

However, no system developed so far is believed to be ideal. The priorart fails to teach coating compositions, effective over a considerableperiod, to destroy algae and fungi.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a coating compositionproviding long-lasting antifouling properties. The composition comprisesan emulsion polymer and a non-metallic algicide that does not react withthe polymer. They are stable emulsions which can be readily applied tosubstrates such as fish netting, wooden shingles and lumber.

Briefly, the compositions contain partially crosslinked polymers andcopolymers of vinyl compounds and from 10 to 50% by weight (based onsolids) of selected quaternary ammonium compounds. The compositions,after coating, contain the quaternary ammonium compoundsmicroencapsulated in the polymer lattices. This encapsulation of thehighly soluble quaternary ammonium compounds retards their migration tothe surface of the coating, thereby enabling the coating to retainbiocidal activity for a long period, over one year, even in a moist orwet environment.

The compositions may contain up to 20% by weight of filler. Exemplaryfillers are calcium carbonate, talc, silica and alumina. Such fillersserve to increase the bulk of the coating composition and as a carrierfor the quaternary ammonium compounds.

The particularly surprising aspect of the present invention is thefinding that a stable emulsion containing a substantial amount ofquaternary ammonium compounds can be formed which has an almostindefinite shelf life at a temperature above 5'C. In addition, thecompositions have good coating and film-forming ability as well assubstantial flexibility, the latter being enhanced by the presence ofthe quaternary ammonium compounds.

DETAILED DESCRIPTION OF THE INVENTION

The emulsion polymers of the invention include polymers and copolymersof vinyl monomers and up to 10% by weight of acrylic monomers. Examplesof the former are vinyl acetate, vinyl chloride, and vinylidenechloride.

The acrylate component may be an alpha,beta-unsaturated carboxylic acidor anhydride such as acrylic, methacrylic, and itaconic acid andanhydride; and an acrylic, an alkyl acrylate or a methacrylate estersuch as ethyl acrylate, isopropyl acrylate, butyl acrylate,tertiary-butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate,isopropyl methacrylate and isobutyl methacrylate.

As noted above, the emulsion polymers of the invention must be partiallycrosslinked. This crosslinking is effected via the appendent hydroxylgroups on the polymer backbone. The crosslinking must be sufficient tomicroencapsulate the quaternary ammonium compound. Where larger amountsof quaternary ammonium compound are desired, fillers such asprecipitated silica are useful. The question of whether the crosslinkingis sufficient may be readily determined by treating the composition withwater and ascertaining whether the quaternary ammonium compound isleached. In order for the encapsulation to be considered satisfactory,the polymer coating must provide algicidal activity for at least oneyear in water at ambient temperatures.

The preferred non-metallic algicides are dialkyldimethyl ammoniumcompounds, preferably the chlorides and the acetates. The aforementionedcompounds can be used alone or in combination with N-alkylbenzyldimethylammonium chloride or acetate. In both instances, there are preferablyfrom 8 to 16 carbon atoms in each alkyl chain.

Specific examples of the dimethyldialkyl ammonium compounds aredioctyldimethyl ammonium chloride, didecyldimethyl ammonium chloride,didodecyldimethyl ammonium chloride, octyldecyldimethyl ammoniumchloride, decyldodecyldimethyl ammonium acetate, and dihexadecyldimethylammonium acetate. Examples of the alkylbenzyldimethyl ammonium compoundsare decylbenzyldimethyl ammonium chloride, decylchlorobenzyldimethylammonium chloride, and dodecyldichlorobenzyldimethyl ammonium acetate.

As noted above, the dialkyldimethyl ammonium compound may be used aloneor in an admixture with a benzalkonium compound. The dialkyldimethylcompound may be used in admixture with up to 3.5 times as much by weightof the benzalkonium chloride. Preferably, the ratio of the benzalkoniumcompound to the dialkyl should be about 1:2 by weight.

In the preparation of the composition of the invention, processconditions must be carefully controlled so as to avoid thedestabilization of the emulsion, that is, the coagulation of the latexparticles. To achieve this result, the quaternary ammonium compound mustbe diluted to a solids content of not more than 50% by weight. Thelatex, in turn, must be diluted so that the solids concentration is lessthan 50%. In addition, the pH of the latex is adjusted to the alkalinerange, preferably to a pH of from 6 to 11, most preferably from 8 to 9.This may readily be accomplished by the addition of alkaline materialsuch as sodium or ammonium hydroxide, sodium carbonate, or sodiumacetate. Thereafter, the diluted latex is mixed slowly for a period offrom 30 min. to 1 hr. at ambient temperature.

The addition of the diluted quaternary ammonium compound to the emulsionalso must be done slowly with particular care to avoid coagulation.Mixing must be done slowly during the addition and subsequently for atotal of at least 5 hours. Failure to control the mixing will result inthe formation of foam, excessive shear and destabilization of the latex.

If a filler is employed in the formulation, this is added to thequaternary ammonium compound prior to its introduction into the dilutedlatex to facillitate the absorption of the quaternary on the fillersurface.

The formulation of the invention may be applied to the substrate by anyof the conventional methods with the understanding that high shearshould be avoided. For example, for fish net treating, dipping isemployed. For other applications, dipping, spraying and brushing can beused.

In order to demonstrate more clearly the instant invention, using theprocedure set forth above, the following formulations are prepared, theamounts being by weight of solids:

                                      TABLE I                                     __________________________________________________________________________               Example No.                                                        Ingredients                                                                              1  2  3  4  5  6   7  8   9   10 A  B  C                           __________________________________________________________________________    Ethylvinylacetate                                                                        50 65 75 60 60 60  60 70  58.5                                                                              52 100                                                                              90 90                          (EVA) copolymer                                                               Vinyl-acrylic                                                                            -- -- --  5 --   2.5                                                                             -- --  --  -- -- 10 --                          copolymer                                                                     Polyvinyl chloride                                                                       -- -- -- --  5   2.5                                                                             -- --  --  -- -- -- 10                          acrylic copolymer                                                             Dioctyldimethyl                                                                          -- -- -- -- -- --   5   2.5                                                                             9    8 -- -- --                          ammonium chloride                                                             Octyldecyldimethyl                                                                       -- -- -- -- -- --  10  5  --     -- -- --                          ammonium chloride                                                             Didecyldimethyl                                                                          50 35 25 35 35 35   5   2.5                                                                             13.5                                                                              12 -- -- --                          ammonium chloride                                                             N(C.sub.12, C.sub.14, C.sub.16)alkyl                                                     -- -- -- -- -- --  20 20  9    8 -- -- --                          dimethylbenzyl                                                                ammonium chloride                                                             Filler, 1 pt CaCO.sub.3,                                                                 -- -- -- -- -- --  -- --  10  20 -- -- --                          9 pts silica                                                                  Parts of solids                                                                          100                                                                              100                                                                              100                                                                              100                                                                              100                                                                              100 100                                                                              100 100 100                                                                              100                                                                              100                                                                              100                         by weight                                                                     __________________________________________________________________________

FORMULATIONS

Examples 1 to 10 demonstrate preferred embodiments of the invention. Ineach case a stable milky emulsion is formed. After one year only aminimal amount of separation occurs. Examples A to C are comparativeformulations.

EXAMPLE 1

625 g of 80% solids didecyldimethyl ammonium chloride are dissolved in375 g of water to obtain 50% solution of quaternary ammonia.

In another vessel 893 g of latex (EVA, 56% solids, Swift Adhesive 6113,a registered trademark of Swift Adhesives) is diluted by 107 g of waterto 50% emulsion. The pH of the emulsion is adjusted with ammonium to 9and kept under continuous mixing for 30 minutes. After this time, thesolution of quaternary ammonium compound is added very slowly undercontinuous mixing. The mixing is continuously provided for 5 hours. Astable emulsion is formed and the product is ready for use.

EXAMPLE 2

As per Example 1, except 438 g didecyldimethyl ammonium chloride isdissolved in 263 g of water and 1160 g EVA latex are diluted with 140 gof water.

EXAMPLE 3

As per Example 1, except 313 g of didecyldimethyl ammonium chloride aredissolved in 188 g of water and 1339 g of EVA latex are diluted with 161g of water.

EXAMPLE 4

As per Example 2, except 1071 g EVA latex and 89 g vinyl-acrylic latex(UCAR 503, registered trademark of Union Carbide Corp.) are diluted with140 g of water.

EXAMPLE 5

As per Example 4, except that 89 g of polyvinyl chloride-acrylic latex(UCAR 516, registered trademark of Union Carbide Corp.) are used insteadof vinyl acrylic latex.

EXAMPLE 6

As per Example 4, except that 45 g of vinyl acrylic latex and 45 g ofpolyvinyl chloride-acrylic latex are used.

EXAMPLE 7

Using the process described in Example 1, 1071.3 g of EVA latex arediluted with 128.7 g of water and then blended with 250 g of (C₈,C₁₀)dialkyldimethyl ammonium chloride (Bardac 2080, a registered trademarkof Lonza Inc.) and 250 g of (C₁₂,C₁₄,C₁₆) dialkyldimethylbenzyl ammoniumchloride (Barquat MB-80, a registered trademark of Lonza Inc.). Thealkyl distribution of Bardac 2080 is 1 part dioctyl, 2 parts octyldecyland 1 part didecyl, while that fo the Barquat MB₋₋ 80 is C₁₂ -40%, C₁₄-50% and C₁₆ -10%.

EXAMPLE 8

As per Example 7, except that 1249.9 g of EVA latex are diluted with150.2 g of water, and 120 g (C₈,C₁₀)dialkyldimethyl ammonium chloride(Bardac 2080) and 240 g of (C₁₂,C₁₄,C₁₆)dialkyldimethylbenzyl ammoniumchloride (Barquat MB-80) are used.

EXAMPLE 9

112.5 g of 80% solids dioctyldimethyl ammonium chloride, 169 gdidecyldimethyl ammonium chloride and 113 g(C₁₂,C₁₄,C₁₆)dialkyldimethylbenzyl ammonium chloride are dissolved inseparate vessel in 338 g of water to obtain 50% QAC solution. To thissolution 100 g of precipitated silica are slowly added and mixed for 30minutes. In another vessel 1044 g of EVA latex are diluted by 97 g ofwater. The process is continued as per Example 1.

EXAMPLE 10

As per Example 9, except 100 g of dioctyldimethyl ammonium chloride, 150g didecyldimethyl ammonium chloride and 100 g(C₁₂,C₁₄,C₁₆)dialkyldimethylbenzyl ammonium chloride are dissolved in300 g of water and 200 g of precipitated silica are used. In a secondvessel 928 g of EVA latex and 86 g of water are used.

COMPARATIVE EXAMPLES Example A

1786 g of EVA latex are diluted by 215 g of water and continuously mixedfor 5 hours.

Example B

1607 g of EVA latex and 179 g of vinyl-acrylic (UCAR 503) latex arediluted by 215 g of water and continuously mixed for 5 hours.

Example C

As per Example B but, instead of vinyl-acrylic latex (UCAR 516),polyvinyl chloride-acrylic copolymer is used.

In Comparative Examples A to C, no quaternary ammonium compound ispresent. The emulsions are stable.

APPLICATIONS

The following Examples 11 to 15 show the application of the compositionsof the invention. The results obtained are shown in Tables II to IVbelow.

EXAMPLE 11

Sixty-five pieces of 12"×24", 1" sq. opening, fish farm nylon 2" nettingare dipped in mixtures made as per Examples 1 to 10 and A to C at 20' C.(five pieces each, dried for 2 hours at 20' C. and cured for 2 days atthe same temperature). Thereafter, three pieces coated with the mixturefor each of the Examples plus three uncoated pieces are submerged in theocean in Patricia Bay, Vancouver Island, B.C., Canada; and two of eachtreatment and two uncoated pieces are submerged in the ocean in the Bayof Fundy, New Brunswick, Canada. The tests were commenced in mid-summer.

Tables II A and II B show the results of the treatment. The formulationsof Examples A through C are emulsion polymers free of quaternaryammonium compound. The final run shows the observations on an untreatednet. The results are reported in 30-day intervals for a period of oneyear.

                                      TABLE IIA                                   __________________________________________________________________________    Location: Patricia Bay B.C.                                                   Max. water temperature 22° C.                                                 DAYS                                                                   EXAMPLE                                                                              30                                                                              60                                                                              90                                                                              120                                                                              150                                                                              180                                                                              210                                                                              240                                                                              270                                                                              300                                                                              330                                                                              360                                      __________________________________________________________________________    1      0 0 0 0  0  0  0  0  0  1  1  2                                        2      0 0 0 0  0  0  0  0  0  0  0  1                                        3      0 0 0 0  0  0  0  0  0  0  1  2                                        4      0 0 0 0  0  0  0  0  0  0  0  1                                        5      0 0 0 0  0  0  0  0  0  0  0  1                                        6      0 0 0 0  0  0  0  0  0  0  0  0                                        7      0 0 0 0  0  0  0  0  0  0  0  1                                        8      0 0 0 0  0  0  0  0  0  1  2  2                                        9      0 0 0 0  0  0  0  0  0  0  0  0                                        10     0 0 0 0  0  0  0  0  0  0  0  0                                        A      3 4 5 Completely plugged                                               B      3 4 5 Completely plugged                                               C      3 4 5 Completely plugged                                               Untr.  3 4 5 Completely plugged                                               __________________________________________________________________________     0 -- No growth                                                                1 -- Very slight growth                                                       2 -- Slight growth                                                            3 -- Growth not restricting flow of water                                     4 -- Growth restricting flow of water                                         5 -- Prolific growth  plugging the netting                               

The above data clearly show the efficacy of the coating compositions ofthe invention in preventing the growth of algae on aquiculture fishnetting.

                                      TABLE IIB                                   __________________________________________________________________________    Location: Bay of Fundy N.B.                                                   Max. water temperature 13° C.                                                 DAYS                                                                   EXAMPLE                                                                              30 60 90                                                                              120                                                                              150                                                                              180                                                                              210                                                                              240                                                                              270                                                                              300                                                                              330                                                                              360                                    __________________________________________________________________________    1      0  0  0 0  0  0  0  0  0  1  1  1                                      2      0  0  0 0  0  0  0  0  0  0  0  1                                      3      0  0  0 0  0  0  0  0  0  0  1  1                                      4      0  0  0 0  0  0  0  0  0  0  0  0                                      5      0  0  0 0  0  0  0  0  0  0  0  0                                      6      0  0  0 0  0  0  0  0  0  0  0  0                                      7      0  0  0 0  0  0  0  0  0  0  1  1                                      8      0  0  0 0  0  0  0  0  0  1  2  2                                      9      0  0  0 0  0  0  0  0  0  0  0  0                                      10     0  0  0 0  0  0  0  0  0  0  0  0                                      A      2-3                                                                              3-4                                                                              5 Completely plugged                                             B      3  4  5 Completely plugged                                             C      3  4  5 Completely plugged                                             Untr.  3  4  5 Completely plugged                                             __________________________________________________________________________     0 -- No growth                                                                1 -- Very slight growth                                                       2 -- Slight growth                                                            3 -- Growth not restricting flow of water                                     4 -- Growth restricting flow of water                                         5 -- Prolific growth  plugging the netting                               

The above data clearly show the efficacy of the coating compositions ofthe invention in preventing the growth of algae on aquiculture fishnetting.

EXAMPLE 12

Material from Example 1 is diluted 1 to 5 with water and sprayed over anew shake roof of one of two sheds build side by side on northern edgeof the 50 ft. high forest growth in Whonnock, British Columbia. Bothsheds are in full shade all year round. The second shed has an untreatedshake roof made from hand cut shakes of 80 year old Western Red Cedar(second growth). Table III show the results of the experiments:

                                      TABLE III                                   __________________________________________________________________________    Months                                                                        2       4   6   8 10                                                                              12                                                                              14                                                                              16                                                                              18                                                                              20                                                                              22                                                                              24                                                                              26                                                                              28                                        __________________________________________________________________________    Treated                                                                             0 0   0   1 1 1 1 1 1 1 1 1 1 1                                         roof                                                                          Untreated                                                                           1 2 + 3                                                                             2 + 4                                                                             5 Roof covered with algae growth                              roof                                                                          __________________________________________________________________________     0 -- No change of color                                                       1 -- Slight change of color                                                   2 -- Gray color                                                               3 -- Slight growth of algae (covers up to 15% of area)                        4 -- Growth of algae (covers up to 60% of area)                               5 -- Full growth of algae (covers over 80% of area)                      

The shake roof treated with material from Example 1, during a period ofover two years, changed only slightly in 8 months. Thereafter, the colordid not change for the duration of the experiment (28 months).

The untreated shake roof started to slowly change the color in thesecond month. At the end of the third month the color changed to greyishand the first algae growth began to show. After six months exposure tothe environment, the algae qrowth covered approximately 55 to 60% of thearea of the roof. After the eighth month, the shakes were green and soonafter that, moss started to grown.

EXAMPLE 13

Part A

Materials from Example 1 to 8 and A to C are diluted 1 to 15 with waterand applied to the freshly cut pieces 1/4"×3/4"×4" of Douglas Fir(Pseudotauga mentiezi Var. Mendiezi) wood as per ASMT D 4445-84. Thewood surfaces are inoculated by the following sap stain fungi:

1) Diplodia Natalensis P. Evans (ATCC #34643)

2) Caratocystis Pilifera (ATCC #15457)

3) Aureobasidum Pullulans (ATCC #16624); mold fungi:

1) Trichoderma Pseudokoningii (ATCC #28801)

2) Cephaloascus Fragrans (ATCC #12091)

3) Gliocladium Roseum (ATCC #10521).

Part B

Materials from Examples 1 to 8 and A to C are diluted 1 to 15 with waterand each material sprayed on 200 board feet of freshly cut 2"×4" lumber,marked and immediately bundled together with untreated lumber randomlyplaced in the bundle. Table IV shows the results of the tests describedin Parts A and B:

                  TABLE IV                                                        ______________________________________                                        PETRI DISH - Days      SAWMILL - Weeks                                        Example 30    60    90  120  150  180  8   14   20  26                        ______________________________________                                        1       0     0     0   0    0    0    0   0    0   0                         2       0     0     0   0    0    1    0   0    0   0                         3       0     0     0   0    0    1    0   0    0   0                         4       0     0     0   0    0    1    0   0    0   0                         5       0     0     0   0    0    1    0   0    0   0                         6       0     0     0   0    0    0    0   0    0   0                         7       0     0     0   0    0    0    0   0    0   0                         8       0     0     0   0    1    2    0   0    1   1                         A       5     5     5   5    5    5    5   5    5   5                         B       5     5     5   5    5    5    5   5    5   5                         C       5     5     5   5    5    5    5   5    5   5                         Uncoated                                                                              5     5     5   5    5    5    5   5    5   5                         ______________________________________                                         0 -- No discoloration, no growth                                              1 -- single less as 1 mm spot                                                  5 -- Discoloration and green, yellow and white fungal growth.           

The ASTM C 4445-84 requires 2 to 4 weeks incubation before theevaluation. Because of the excellent results with the composition of theinventions, the time and duration of the experiment was extended to 180days. The untreated and latex treated test pieces first started showingdiscoloration in three days and growth of the fungi at middle of secondweek.

The lumber on the sawmill was first checked after three weeks. Even atthat time, the untreated and latex treated surfaces which were not incontact with surface treated with solutions from Examples 1 to 8 showedunacceptable discoloration. Treated surfaces remained absolutely clearfor the duration of six month experiments. This test was compared with anormal production sawmill run, where the lumber was treated with Copper8 Quinoline compound. The latter started showing the growth in fourweeks. A sawmill run with Borax sodium carbonate showed immediate changein the wood color (uneven brown) and growth of fungi in 8 weeks.

EXAMPLE 14

Two sets of 20 g of materials as per Example 1 to 10 and A to C (26total) are poured into Petri dishes and let dry and cure for three days.After curing, the layer of material is removed from dishes and is cut to2"×2"×1/16" pieces (4" sq.) and tested for leaching. The test pieces areinitially weighed on analytical scales and the weight recorded. The testpieces are leached in continuously flowing water for twelve weeks and,during this period, periodically dried and weighed. Data is collectedafter the first 24 hours and then weekly during the test period. Theleaching of the active ingredience, in % by weight, is calculated andreported in Table V:

                                      TABLE V                                     __________________________________________________________________________    Leaching of Active Ingredience                                                Example                                                                            24h                                                                              1w 2w 3w 4w 5w 6w 7w 8w 9w 10w                                                                              11w                                                                              12w                                  __________________________________________________________________________    1     11.5                                                                            3  3  2.8                                                                              2.7                                                                              2.5                                                                              2.4                                                                              2.4                                                                              2.4                                                                              2.4                                                                                2.3                                                                              2.3                                                                              2.3                                2    8  2.6                                                                              2.5                                                                              2.5                                                                              2.4                                                                              2.4                                                                              2.3                                                                              2.3                                                                               2.25                                                                            2.2                                                                                2.1                                                                              2.1                                                                            2                                    3    5  2.3                                                                               2.25                                                                             2.25                                                                             2.25                                                                            2.2                                                                              2.2                                                                              2.1                                                                              2.1                                                                              2  2  2    1.9                                4      6.5                                                                            2.4                                                                              2.4                                                                              2.3                                                                              2.3                                                                              2.3                                                                               2.25                                                                            2.2                                                                              2.2                                                                              2.1                                                                              2  2  2                                    5      6.5                                                                            2.4                                                                              2.4                                                                              2.3                                                                              2.3                                                                              2.3                                                                              2.2                                                                              2.2                                                                              2.1                                                                              2.1                                                                              2  2  2                                    6      4.5                                                                            2.3                                                                              2.2                                                                              2.2                                                                              2.2                                                                              2.1                                                                              2.1                                                                              2.1                                                                              2.1                                                                              2  2  2    1.9                                7    10 2.8                                                                              2.8                                                                              2.7                                                                              2.7                                                                              2.4                                                                              2.4                                                                              2.3                                                                              2.3                                                                              2.3                                                                                2.3                                                                              2.3                                                                              2.2                                8    7  2.5                                                                              2.5                                                                              2.4                                                                              2.4                                                                              2.4                                                                              2.3                                                                              2.3                                                                              2.2                                                                              2.1                                                                                2.1                                                                            2  2                                    9    6  2.4                                                                              2.4                                                                              2.3                                                                              2.3                                                                              2.3                                                                              2.2                                                                              2.2                                                                              2.2                                                                              2.1                                                                              2  2  2                                    10   6  2.3                                                                              2.3                                                                              2.3                                                                              2.2                                                                              2.2                                                                              2.1                                                                              2.1                                                                              2.1                                                                              2  2  2    1.9                                A    0  0  0  0  0.1                                                                              0  0  0  0  0  0    0.1                                                                            0                                    B    0  0  0  0  0  0  0.1                                                                              0  0  0  0  0  0                                    C    0  0  0  0  0  0  0.1                                                                              0  0  0  0  0  0                                    __________________________________________________________________________

We claim:
 1. A method of forming an antifouling composition whichcomprises:forming a first solution containing not more than 50% byweight of a non-metallic algicide consisting essentially of adialkyldimethyl quaternary ammonium compound alone or in combinationwith an alkylbenzyldimethyl ammonium compound; forming a second solutioncontaining less than 50% by weight of a partially crosslinked emulsionpolymer selected from vinyl acetate homopolymer, vinyl acetate-acryliccopolymer, vinyl acetate-ethylene copolymer, and acrylic-polyvinylchloride copolymer; adjusting the pH of said second solution to thealkaline range and thereafter stirring said second solution; and slowlyadding said first solution to said second solution while mixing saidsecond solution at low shear to avoid the formation of foam and thecoagulation of said emulsion polymer.
 2. The method of claim 1 whereinthe second solution is stirred for at least 5 hours during and after theaddition of the first solution.
 3. The method of claim 1 wherein afiller is added to the first solution prior to admixture with the secondsolution.
 4. A coated article which comprises a substrate coated with anantifouling coating composition comprising a partially-crosslinkedpolymer selected from a vinyl acetate homopolymer; a vinylacetate-acrylic copolymer; a vinyl acetate-ethylene copolymer; and anacrylic-polyvinyl chloride copolymer; anda non-metallic algicideconsisting essentially of a quaternary ammonium compound having methylgroups and two alkyl groups alone or in combination with a secondquaternary ammonium compound having methyl groups, an alkyl group and abenzyl group, said algicide being encapsulated in said polymer and beingcapable of being leeched from said composition during submersion.
 5. Thecoated article of claim 4 wherein the coated article is a fish net orbuoy.
 6. The coated article of claim 4 wherein the substrate is a porousarticle.
 7. The coated article of claim 6 wherein the substrate is woodor concrete.